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Hack 37. Grab Attention
Sudden movement or light can grab your attention, thanks to a second region for visual processing. What are you paying attention to? These words? In a minute it could switch to a friend or to making coffee or to the person on the bus who just stood up and you noticed out of the corner of your eye. We don't pay attention to everything we see or experience. Following two conversations at the same time is hard, even though we hear both perfectly well, and, likewise, it's simply not possible to read every word on the page of a book simultaneously, although they're all in plain view. While your senses work overtime to provide as much input as possible, there's a bottleneck in the brain's limited capacity for attention. So we consciously decide which line of text to focus on and read across and down the page, line by line. And this happens at the expense of all the other stimuli we could have attended to, such as the color of the walls or the traffic noise from the road outside. Choosing what to give attention to is voluntary...mostly. But attention can also be captured. In Action Stand so that you're facing a crowded scene. Watching a crowded theater settle down is ideal. A busy street corner is a good choice, too. A TV screen or video game will do as well, as long as there's a lot going on in the frame. Don't try to direct your attention; just let it wander and feast your eyes on the full field of view. Notice that when a person waves, or stands up, your attention is grabbed and snaps to focus on the person's position. It's not so much that you notice the waving or standing up itself; the event simply captures your attention and you properly focus on that place a fraction of a second afterward. Since you're relaxed, your attention soon drifts away, until someone else moves and captures it again. Your attention scintillates across your whole field of view, darting from point to point. How It Works After visual information leaves the eye, it doesn't just go to one place for processing; the signal divides. Our conscious appreciation of visual information is provided by processing done in the visual cortex. It sits at the back of the brain in the area called the occipital lobe and performs what we typically associate with the job of vision: figuring out exactly what shape the thing you're looking at is, what color, if it's moving, then in what direction and how fast, what it means, and so onproviding the raw information needed to put names to faces and avoid stepping in front of a car while crossing a road. Attention capture, on the other hand, relies on processing done by a region of the brain called the superior colliculus. It gets a copy of the same visual information the visual cortex does from the retina, but processes it in a different way. This region is evolutionarily ancient, which means the basic structure was established and refined in brains far simpler than our own, through many species of animals. (Rather than relegating it to second place, fish and amphibians do most of their visual processing with their equivalent of the superior colliculus, called the optic lobe.) So as one might expect, it's not particularly sophisticated, compared to the visual cortex. And it doesn't use much of the information it receives; the superior colliculus looks at a black-and-white world through frosted glass. Then again, it doesn't need much. This processing is for rapid response, when it appears something potentially dangerous is happening and urgent action is needed quicker than the complex visual cortex can respond. It's just useful enough to guide reflex movements, tell the head and body to orient in a particular direction, and force attention to snap to important-seeming events.
That's what's going on when attention is captured. There's a sudden movement and the rapid response bit of your brain says, "Hey, I don't know what that was, but pay it some attention and figure out what to do in case it attacks us." Looking at the crowd, your attention darts around automatically because this bit of your brain feels startled enough to interrupt consciousness every time somebody waves suddenly. When you're sitting in a darkened theater, absorbed in the dialog on stage, think about what happens when a door opens at the side of the room. The sudden appearance of light grabs your attention. If it happens again, despite the fact that you know you're not interested, it still grabs your attention and demands a response. It's distracting. That's the automatic nature of attention capture coming into play. On the upside, that bright light flashing in the corner of your eye could well be a ray of sunlight being revealed as a large dangerous something lumbering out of the shadows toward you. The automatic capture of attention serves to orient conscious perception in important directions.
Events that capture attention include the two already mentioned: sudden light (actually, a sudden change in contrast) and sudden movement. In keeping with the purpose of facilitating rapid response, it's only new movement that captures attention. Ongoing motion, like a moving car or a walking person, doesn't trigger the automatic shift in attention. Two other triggers provide hints as to what else our brains regard as so critical to survival that they deserve a rapid response. One is an object appearing abruptly. In general, our brains give special treatment to objectsas opposed to backgrounds and shadows, which are given less attention. This makes sense, as objects such as other people, animals or food usually require a response of some kind. There are even dedicated routines to object tracking [Hack #36] . An extra person, rock, or car in the sceneespecially if it appears suddenlyis likely to be a big deal, so attentional capture is triggered.1 John Eastwood and his colleagues also suggest another trigger that is worth mentioning as it shows just how deep our social nature goes. The trigger here is facial expression.2 Eastwood's team made simple line-drawing faces, happy and sad ones, and asked people to count certain of the lines that made up the drawings. When the drawings were upside-down, so they were unrecognizable as faces, people did the counting exercise easily. But when the drawings were the right way up, counting took longer for drawings of faces that displayed negative emotions rather than for drawings of positive expressions. Why? The team's conclusion is that negative expressionssad or angry facesdistract you, in just the same way as light through a theater door grabs your attention away from the main action. End Notes 1. Enns, J. T., Austen, E. L., Di Lollo, V., Rauschenberger, R., & Yantis, S. (2001). New objects dominate luminance transients in setting attentional priority. Journal of Experimental PsychologyHuman Perception and Performance, 27(6), 1287-1302. 2. Eastwood, J. D., Smilek, D., & Merikle, P. M. (2003). Negative facial expression captures attention and disrupts performance. Perception & Psychophysics, 65(3), 353-358. See Also · A curious side effect of having two regions devoted to visual processing is when the conscious region, the visual cortex, is damaged but the other, automatic one remains intact. Blindsight emerges, in which a person believes herself to be blind but is somehow able to reach directly for a flashing light accurately every time. Visual information has reached the person subconsciously, and she puts it down to guesswork. Professor Ramachandran covers blindsight, and more, in the second of his series of BBC Reith Lectures from 2003, "The Emerging Mind" (http://www.bbc.co.uk/radio4/reith2003/lecture2.shtml).
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Hack 38. Don't Look Back!
 
Your visual attention contains a basic function that puts the dampers on second glances.
There are layers and layers of functions and processing in the brain. Oneattentionis a collaborative exercise between voluntary application of attention and automatic mechanisms to snap attention to where it's needed [Hack #37] . Even the voluntary application of attention is a negotiation with what evolution has taught the brain is most sensible. In particular, the brain doesn't like to return attention to a place or object it has just left. This phenomenon is called inhibition of return.
3.6.1. In Action
Like negative priming [Hack #42], which is how contextual features are suppressed from attention, inhibition of return is such a low-level effect that it's hard to show without precision timing equipment. Again, just like those other effects, it turns up in all kinds of cases because attention is so widely employed.
Imagine you're taking part in an experiment in which an icon flashes up on a screen and you have to touch that position. It'll take you longer to move and touch the icon if some other icon had previously, and recently, been in that position.
Inhibition doesn't kick in immediately. Let's say you're playing Whack-A-Mole,1 in which moles emerge from holes and you have to hit them with a hammer. A hole could light up momentarily before the mole appears. This would be a prime candidate for the inhibition-of-return effect. If the brightening occurs very shortly before the mole appears, only a fifth of a second or so, it serves to draw your attention to that place and you'll actually respond to the mole faster.
If, on the other hand, the brightening occurs and then there's a longer pausemore than a fifth of a second and up to 3 or 4 secondsthat's enough time for your attention to be dragged to the brightness change then shift away again. Inhibition of return kicks in, and when the mole appears in that same spot, you have to overcome the inhibition. It'll take longer for you to react to the mole (although it's not likely you'll miss it. Reaction time increases only on the order of a twentieth of a second or soenough to make a difference in some circumstances, but hard to spot.) One caveat: if the brightening happens before the mole pops up every single time, you're going to learn that pattern and end up being better at whacking the mole every time instead.
3.6.2. How It Works
The big question is why this happens. One possibility is that it's because we prefer novelty and want to suppress distracting stimuli. An attention-grabbing event is good if it's useful, but if it's not the event we're looking for, then we're better off focusing our attention elsewhere in the future and ignoring that distracting location.
Raymond Klein, in his review paper "Inhibition of Return,"2 gives the example of efficient foraging for food. He suggests that potential locations that have been found bare should be remembered as places to be avoided, and this acts as a mechanism to orient toward novel locations. This could be used just standing in one place and looking ahead to find edible plants on the ground. For a task like visually searching straight ahead, it would be extremely useful to have a mechanism that allows you to briefly look harder (for a fifth of a second) and helps you to look for novel locations (for a few seconds after).
Current research indicates there may be two ways in which inhibition of return is produced. One is at a very low level, subcortically in the superior colliculus, which does rapid visual processing (but isn't responsible for our conscious visual processing [Hack #13], which takes longer) and helps orient the pupils and body. Indeed, damage to this part of the brain stops inhibition of return from taking place3, at least for stopping the eyes moving back to locations they've previously been.
Inhibition of return could also be triggered by higher-level operations in the allocation of attention. The fact that the inhibition remains in place even when the objects are moving around supports thisit can no longer rely on just eye position. Think of counting a crowd of people when they're all moving around: you're able to do this because you can deselect people who have already been counted. This is the inhibition of return in play.
3.6.3. In Real Life
In fact, that this mechanism crops up in more than one place in the brain points to it being a good, generic solution to tricky search problems, rather than a workaround for some problem specific to a particular function like feature processing. I can see the same strategy coming into play when I'm looking for something I've lost in my house. I'll search one location pretty thoroughly, then move on to the next, and the next, and the next. If someone suggests I return to my first location and look there again, I'm pretty reluctant. After all, I would have found it first time around, right?
If this is a common strategy in search, there are some pointers for interface design. Don't attract people's attention to a place briefly if you really want to grab their attention there shortly after. So if a news ticker on a web site, for example, appears with a flash but then has a 2-second pause before the news appears on it, people aren't going to notice the news coming up. The initial flash will have inhibited their attention returning there for the subsequent few seconds. If something is going to happen, make it happen immediately, not after a brief pause. When people are skimming over stuff, they don't want to have their attention squanderedinhibition of return makes second glances less likely.
3.6.4. End Notes
1. Spy Whack-A-Mole, using Flash (http://www.spymuseum.org/games/mole.html), lets you play the game and simultaneously learn about the past 100 years of spying.
2. Klein, R. M. (2000). Inhibition of return. Trends in Cognitive Science, 4(4), 138-147.
3. Sapir, A., Soroker, N, Berger, A., & Henik, A. (1999). Inhibition of return in spatial attention: Direct evidence for collicular generation. Nature Neuroscience, 2(12), 1053-1054.
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Date: 2015-12-11; view: 733
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